Wink – A framework for RESTful web services from Apache

Apache Wink 1.0 is a complete Java based solution for implementing and consuming REST based Web Services. The goal of the Wink framework is to provide a reusable and extendable set of classes and interfaces that will serve as a foundation on which a developer can efficiently construct applications.
Taken from Apache Wink official site: Click Here
Wink consists of a Server module for developing REST services, and of a Client module for consuming REST services. It cleanly separates the low-level protocol aspects from the application aspects. Therefore, in order to implement and consume REST Web Services the developer only needs to focus on the application business logic and not on the low-level technical details.
REST Web Service design structure

The Wink Server module is a complete implementation of the JAX-RS v1.0 specification. On top of this implementation, the Wink Server module provides a set of additional features that were designed to facilitate the development of RESTful Web services.
The Wink Client module is a Java based framework that provides functionality for communicating with RESTful Web services. The framework is built on top of the JDK HttpURLConnection and adds essential features that facilitate the development of such client applications.

REST in Java

You may want to call the REST web service from Java. Following is the code for a simple Web Service client for the flickr web services interface.

pacage com.vaani.rest; import java.net.HttpURLConnection; import java.net.InetSocketAddress; import java.net.Proxy; import java.net.SocketAddress; import java.net.URL; import javax.xml.parsers.DocumentBuilder; import javax.xml.parsers.DocumentBuilderFactory; import org.w3c.dom.Document; public class FlickrClient {     public static void main(String[] args) {         String flickrURL = "http://api.flickr.com/services/rest/?method=flickr.test.echo&name=value&api_key=[yourflickrkey]";         try {             SocketAddress addr = new InetSocketAddress("[proxy]", 9090);             Proxy proxy = new Proxy(Proxy.Type.HTTP, addr);             URL u = new URL("http://api.flickr.com/services/rest/?method=flickr.test.echo&name=value&api_key=[yourflickrkey]");             HttpURLConnection uc = (HttpURLConnection) u.openConnection(proxy);             uc.setRequestProperty("Accept", "*/*");             uc.setRequestProperty("Accept-Charset", "ISO-8859-1,utf-8;q=0.7,*;q=0.7");             uc.setRequestProperty("Accept-Language", "en-us,en;q=0.5");             uc.setRequestProperty("Keep-Alive", "300");             uc.setRequestProperty("ucection", "keep-alive");             String proxyUser = "[netUserId]";             String proxyPassword = "[netPassword]";             uc.setRequestProperty("Proxy-Authorization", "NTLM " + new sun.misc.BASE64Encoder().encode((proxyUser + ":" + proxyPassword).getBytes()));             DocumentBuilder docBuilder = DocumentBuilderFactory.newInstance().newDocumentBuilder();             Document doc = docBuilder.parse(uc.getInputStream());             System.out.println(doc.getDocumentElement().getTagName());             System.out.println();         } catch (Exception e) {             e.printStackTrace();         }     } }

RESTful Web Service tutorial: An Introduction for beginners

REST is a term coined by Roy Fielding in his Ph.D. dissertation to describe an architecture style of networked systems. REST is an acronym standing for Representational State Transfer. Representational State Transfer(REST), a software architecture style used in developing stateless web services. While this style may be used to describe any distributed framework that uses a simple protocol for data transmission and no other additional data transfer rules, the most common use of REST is on on the Web with HTTP being the only protocol used here. In REST each service (called “resource” in REST) is viewed as resource identified by a URL, and the only operations allowed are the HTTP – GET (Read), PUT (Update), POST(Create) and DELETE (Delete). You can find this style similar in SQL, thinking of a resource as equivalent to a Table. The main features and constraints of REST architectural style are:

• Client-Server: A clear separation concerns is the reason behind this constraint. Separating concerns between the Client and Server helps improve portability in the Client and Scalability of the server components.
• Stateless: All REST resources are required to be stateless. The idea is that the application would be resilient enough to work between server restarts. However, it is not uncommon to see some RESTful web services save states between requests.
• Caching: Caching is allowed, however it is required that “response to a request be implicitly or explicitly labeled as cacheable or non-cacheable”
• As there is no interface definition (like in SOAP), it becomes mandatory for a Client and Server to have a mutual understanding of the messages being transmitted between them.

Given that every resource in a RESTful service is represented by a URL, it is easy to write a client for such a web service.
A lot of companies these days (including Amazon and Yahoo!) are exposing their web services in the form of REST resources. At a high level REST is pretty easy to understand, all you’re doing is exposing a web service in the form of a URL. Users can then query this URL, through HTTP methods like GET and POST. REST calls generally return some type of XML or Object Encoding like JSON.